To ensure proper nutritional support for newborn infants, many doctors and hospitals recommend the use of liquid pediatric nutritional products. Pediatric nutritional products are utilized when breast feeding is not possible for either medical and/or social reasons. Furthermore, even in cases where breast feeding is possible, some mothers prefer the convenience afforded by the use of pediatric nutritional products.
In response to the need for pediatric nutritional products, water, soy and milk-based liquid foods have been developed for bottle feeding in conjunction with a rubber or latex nipple. Since the containers for these products often provide a twelve to eighteen month shelf life, a hermetic seal must be provided across the top of the container. A hermetic seal is one which when in place is impervious to microbiological intrusion and external influence. Presently, the industry provides of the hermetic seals through the use of a glass container, to which is secured by vacuum closure a stamped steel cap having a pre-cut rubber or vinyl plastisol gasket. The container is then subjected to temperatures above the ambient air temperature, and more specifically to retort conditions, whereby the hermetic seal must survive sterilization of the container. Since the glass container and the stamped-steel cap expand a similar amount and since a vacuum is present within the container, the hermetic seal is maintained during the sterilization process.
Due to concerns about material cost, container weight, and breakage, suppliers of pediatric nutritional products have sought to manufacture the nutritional product container from a polymeric substance, such as polypropylene, which is relatively clear, optically, and cost effective as compared to glass. A problem arises in attempting to provide a cap for a plastic container which maintains a hermetic seal during and subsequent to sterilization. Since conventional metal caps and plastics expand by a dissimilar amount, conventional metal caps do not provide a hermetic seal for plastic containers when subjected to retort conditions.
Another problem arises in that the application of heat under retort conditions causes polymer relaxation or shrinkage, especially in the upper neck portion of the container. Injection or extrusion molded bottles are formed by stretching the polymer molecules. The introduction of heat causes those molecules to relax, so as to actually shrink the diameter of the neck. This shrinkage causes additional problems in maintaining a conventional metal cap on a plastic bottle. This shrinkage also prevents the use of a conventional plastic cap on a plastic bottle.
One approach to the above two problems would be to apply a substantial amount of torque when initially capping the bottle, however the amount of torque necessary to maintain a conventional cap in place is so high that a person would not be able to easily twist off the cap following retort in order to feed an infant. Another possible approach would be to fabricate a bottle from a plastic which does not shrink at retort temperatures and can maintain an internal vacuum without distortion, however, the cost of providing such a bottle would be prohibitive.
Yet another possible approach to the providing of a hermetic seal would be to utilize a barrier membrane, such as aluminum foil, such that the integrity of the seal associated with a stamped-steel closure cap would no longer be important. This primary membrane seal would be protected from accidental or premature puncture by an overcap of a conventional design. One type of foil seal is the type which is peelable. However, in dealing with nutritional products subject to spoilage, peelable seals are not optimal for ensuring against spoilage and tamper prevention. Additionally, peelable foils also encounter difficulty surviving sterilization without encountering problems in their removal.
Therefore, a heat-fused metallic seal, which imparts a permanent seal, fused to the container utilizing with conventional membrane sealing technology is desirable. However the use of a heat-fused foil membrane necessitates that the outer cap be removed, followed by the piercing of the membrane seal. The piercing would normally be accomplished by a microbial laden device, such as a pair of scissors or a fingernail, thereby contaminating the pediatric nutritional product with bacteria from a non-sterilized tool or from the hands of a health care worker or parent.
Conventional laminate composites used in the art of heat-fused foil membrane feature a polyester/foil/polypropylene laminate, with the polypropylene layer placed adjacent the plastic bottle, such that the polypropylene fuses to the bottle when subjected to sufficient heat. However, the polyester does not fuse against an adJacent surface. Thus, placement of a plastic cap over the conventional laminate will not result in the bonding of the polyester to the plastic cap, so that the cap can be used on the container and withstand retort conditions. It is thus apparent that a need exists for an improved closure for a pre-filled, membrane-sealed pediatric nutritional product container which provides system seal integrity, as well as permitting the opening of the nutritional products container in a single action motion. It is also apparent that the need exists for an improved closure for plastic containers which permits the container to survive retort conditions.